This invention relates to a thermoplastic resin composition having reduced flammability, which can be molded to form a shaped article having excellent physical properties. Thermoplastic resins such as polypropylene, polystyrene, ABS resin, Nylon, polyester and polycarbonate have a variety of excellent physical properties, and therefore have been used as engineering plastics such as raw materials for mechanical parts of various machines, electrical equipment and parts of motor cars. Recently those engineering plastics have been subjected to a strong desire for security in case of fire, that is flame resistivity, in addition to well-balanced physical and chemical properties. It is currently indispensable to impart flame resistance to a thermoplastic resin, if the resin is to enlarge its use as an engineering plastic.
Heretofore, organic polymers have been made flame resistant by adding a flame retarding agent such as organic halogen compound, phosphorus compounds, large amounts of inorganic materials, and their combination. Generally speaking, however, the addition of flame retarding agents deterioates the physical properties, of the organic polymer especially durability. It is of practical importance to find a good combination of organic polymer and flame retarding agent.
In the case of thermoplastic resins, the above mentioned method using a large amount of inorganic compound has met with difficulties in blending the resin with the flame retarding agent to obtain a uniform mixture. In the use of a phosphorus compound as a flame retarding agent, it is difficult to obtain a mixture containing a sufficient amount of phosphorus compound to impart flame resistance to the resin. For these reasons, the organic halogen compounds are used in actual practice as flame retarding agents solely or together with an auxiliary flame retarding agent such as antimony trioxide.
Among the organic halogen compounds, aliphatic halogen compounds such as chlorinated paraffin and hexabromocyclododecane do not have enough heat-stability. The aliphatic halogen compounds are likely to cause fuming and odors when they are blended with a thermoplastic resin at a temperature higher than 200.degree.C. Such a phenomenon often results in deterioration of the physical properties of the base polymer.
On the other hand, the halogenated aromatic compounds such as decabromodiphenyl and decabromodiphenylether etc. have high heat-stability, and therefore the above mentioned problems scarcely take place on blending with thermoplastic resin. They, however, have a very high melting point and low solubility in resin. For this reason those compounds are likely to cause deterioration of the physical properties of the resin due to its non uniform dispersion in the resin.
Thus, an object of this invention is to provide a thermoplastic resin composition having reduced flammability together with well-balanced physical properties.
Another object of the invention is to impart flame resistance to a thermoplastic resin without deteriorating its physical properties by using a cyanurate combined with a halogenated aromatic compound as a flame retarding agent.